History's verdict

Historians will look back at yesterday's parliamentary debate on Iraq for a range of good reasons. They will look back in order to understand why Britain could go to war with Iraq alongside the United States amid the deep divisions that were again exposed when the votes were counted last night. They will look back to read an impassioned and impressive speech by the prime minister which may give future generations some inkling of how, when so many of his own party opposed his policy so vehemently, Tony Blair nevertheless managed to retain their respect and support. They will look back to read a second clear and eloquent ministerial resignation statement in as many days - this time from the former Home Office minister John Denham. A few may even read yesterday's debate in order to attempt to explain the otherwise inexplicable fact that the Conservative party of 2003 appeared more concerned at such a time to attack the Liberal Democrats than the Labour government.

Mr Blair spoke powerfully. He was serious in tone, respectful to backbenchers, and at times he reached levels of oratory that he rarely achieves in the Commons. He seemed to sense that, though the argument has not been won, it is swinging his way. Yet intensity cannot disguise Mr Blair's failure to respect the arguments which fire the revolt. In particular he remains deaf to the revulsion against the gratuitous actions of the US that Mr Denham put at the centre of his speech (as Robin Cook did on Monday). The US administration, said Mr Denham, seems "to delight in stressing its disdain for international opinion" and in "asserting its right to determine not just the target but the means and the timetable". As the nine-nation opinion poll yesterday shows, it is the Bush administration that has wrecked international resolve - nothing else. Mr Blair simply won't get it. All his troubles stem from Mr Bush.

But the historians will also look at yesterday's debate because it marks a really important moment in constitutional history. Over the centuries, the decision to go to war has rested, first, with kings alone, then with monarchs in the privy council, more recently with the council acting on the advice of the prime minister, sometimes (as in the Falklands war) largely with the cabinet. Yesterday, all this took a fresh twist. Though the formal prerogative power to declare war remains with the Crown, the de facto authority passed yesterday to MPs. By allowing yesterday's debate and vote, the government delivered on a promise. But it also did more than that. It gave parliament the power to stop the war before it begins. Parliament did not take its chance, alas. But it is clear that, had the vote gone against war, British soldiers would not have gone into battle and Mr Blair would have resigned. He said as much at the end of his speech. In its way, this is as significant a shift in constitutional power as anything since the Glorious Revolution. Having made it, there can hardly be any going back. When and if Britain again stands on the brink of war, it will be parliament that decides. It is hard, even on a day such as this, not to regard that as a kind of consolation prize.